Apparatus for correcting solid-state electronic image sensing device

ABSTRACT

A CCD is such that a single image sensing area is produced by performing exposure four times in four areas. Four correction circuits are provided in association with respective ones of the four areas. Four items of image data obtained based upon respective ones of the four areas are input to corresponding correction circuits, which apply a correction to prevent image disturbance at the area boundaries. One frame of image data is generated from corrected image data of respective ones of the areas and the image data is recorded on a memory card.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] This invention relates to an apparatus for correcting asolid-state electronic image sensing device.

[0003] 2. Description of the Related Art

[0004] A solid-state electronic image sensing device such as a CCD iscreated by placing a photomask on a silicon wafer and then exposing thewafer through the photomask. With creation techniques available at thepresent time, it is difficult to create a large-capacity solid-stateelectronic image sensing device, namely one having 20 to 30M pixels, atone time. Usually, exposure is performed multiple times, i.e., in eachof a plurality of different areas of the CCD.

[0005] Owing to the fact that exposure is performed multiple times, thelevel of a video signal when the signal is read out of the solid-stateelectronic image sensing device differs from one area to another.

SUMMARY OF THE INVENTION

[0006] Accordingly, an object of the present invention is to correct thelevel of a video signal that differs from area to area of a solid-stateelectronic image sensing device.

[0007] According to the present invention, the foregoing object isattained by providing an apparatus for correcting a solid-stateelectronic image sensing device, comprising: a solid-state electronicimage sensing device, which is created by dividing an image sensing areainto a plurality of areas, for outputting image data representing theimage of a subject by sensing the image of the subject; acorrection-value memory for storing correction values in associationwith respective ones of the plurality of areas of the solid-stateelectronic image sensing device; and an image-data correction unit forcorrecting image data, which is obtained based upon respective ones ofthe plurality of areas from among the image data that is output from thesolid-state electronic image sensing device, using correspondingcorrection values from among the correction values stored in thecorrection-value memory.

[0008] The present invention also provides a control method suited tothe above-described apparatus for correcting a solid-state electronicimage sensing device. Specifically, the present invention provides amethod of controlling an apparatus for correcting a solid-stateelectronic image sensing device, which is created by dividing an imagesensing area into a plurality of areas, for outputting image datarepresenting the image of a subject by sensing the image of the subject,the method comprising a step of correcting image data, which is obtainedbased upon respective ones of the plurality of areas from among theimage data that is output from the solid-state electronic image sensingdevice, using corresponding correction values from among correctionvalues that have been stored in association with respective ones of theplurality of areas of the solid-state electronic image sensing device.

[0009] In accordance with the present invention, correction values arestored in association with respective ones of a plurality of areas of asolid-state electronic image sensing device. Image data is output fromthe solid-state electronic image sensing device. Image data obtainedbased upon respective ones of the plurality of areas is corrected bycorresponding correction values from among the correction values thathave been stored in association with the plurality of areas.

[0010] The present invention makes it possible to correct thevideo-signal level that differs from area to area as a result of thesolid-state electronic image sensing device having been created byperforming exposure multiple times in on a per-area basis.

[0011] In a case where there are a plurality of the correction-valuememories associated with respective ones of the plurality of areas, theapparatus would further comprise: a plurality of correction circuitscorresponding to the plurality of correction-value memories; and acontrol unit for applying image data obtained based upon respective onesof the plurality of areas from among the image data output from thesolid-state electronic image sensing device to corresponding correctioncircuits from among the plurality of correction circuits, andcontrolling the correction circuits so as to correct the image datausing corresponding correction values from among the correction valuesthat have been stored in the plurality of correction-value memories.

[0012] Further, the solid-state electronic image sensing device mayinclude a solid-state electronic image sensing element, which is createdby dividing an image sensing area into a plurality of areas, foroutputting a video signal representing the image of a subject by sensingthe image of the subject; and a plurality of analog/digital convertingcircuits provided in association with the plurality of areas forconverting, to respective ones of items of image data, video signalsobtained based upon respective ones of the plurality of areas from thevideo signal output from the solid-state electronic image sensingelement.

[0013] Other features and advantages of the present invention will beapparent from the following description taken in conjunction with theaccompanying drawings, in which like reference characters designate thesame or similar parts throughout the figures thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014]FIG. 1 is a diagram illustrating an image sensing area of a CCD;

[0015]FIG. 2 is a graph illustrating a difference in level produced at aboundary between areas;

[0016]FIG. 3 is a block diagram illustrating the electrical structure ofa digital still camera according to an embodiment of the presentinvention;

[0017]FIG. 4 is a flowchart illustrating correction processing accordingto this embodiment; and

[0018]FIG. 5 is a block diagram illustrating the electrical structure ofa digital still camera according to another embodiment of the presentinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Preferred embodiments of the present invention will now bedescribed in detail with reference to the drawings.

[0020] When a CCD is created, a photomask is placed on a silicon waferand the wafer is exposed through the photomask. It is difficult tocreate a large-capacity CCD (e.g., one having 20 to 30M pixels or more)at one time. Usually, exposure is performed in each of a number ofdifferent areas of the CCD, namely multiple times per CCD.

[0021]FIG. 1 is a diagram illustrating the image sensing area of alarge-capacity CCD.

[0022] As shown in FIG. 1, a large-capacity CCD 1 has an image sensingarea 2 in which a plurality of areas A to D have been defined. Thelarge-capacity CCD 1 is created by performing exposure in each of theplurality of areas A to D.

[0023] By forming the image of a subject on the image sensing area 2 ofthe large-capacity CCD 1 using an imaging lens or the like, a videosignal representing the image of the subject is output by the CCD 1.

[0024]FIG. 2 is a graph illustrating the level of the video signalobtained from the image sensing area 2 along line II-II in FIG. 1.

[0025] If the large-capacity CCD 1 having the image sensing area 2 iscreated by performing exposure multiple times in each of the areas A toD, a difference in level or step 20 is produced in the video signal atthe boundary between areas despite the fact that the levels of the videosignal should coincide at the boundary.

[0026] A digital still camera according to this embodiment is so adaptedthat the difference in level produced at the boundary between areas iscorrected.

[0027]FIG. 3 is a block diagram illustrating the electrical structure ofa digital still camera according to this embodiment.

[0028] As shown in FIG. 3, the digital still camera is provided withfour, i.e., first to fourth, correction circuits 15A, 15B, 15C and 15Dcorresponding to the four areas A to D of the image sensing area 2 ofCCD 1. The four correction circuits 15A, 15B, 15C and 15D correct thelevels of the video signals output from respective ones of the areas A,B, C and D in image sensing area 2. The correction circuit 15A includesa CPU 5A, a correction-value memory 6A and an SDRAM 7A. Similarly, thecorrection circuit 15B includes a CPU 5B, a correction-value memory 6Band an SDRAM 7B, the correction circuit 15C includes a CPU 5C, acorrection-value memory 6C and an SDRAM 7C, and the correction circuit15D includes a CPU 5D, a correction-value memory 6D and an SDRAM 7D.

[0029] Data representing correction values for correcting the leveldifference of the video signals produced by the areas A, B, C and D inthe manner described above is stored in the correction-value memories6A, 6B, 6C and 6D in association with the areas A, B, C and D. Further,as will be described later, the CPUs 5A, 5B, 5C and 5D are so engineeredas to store temporarily, in the SDRAMs 7A, 7B, 7C and 7D, image dataoutput from the corresponding areas A, B, C and D from among the imagedata output from an analog/digital converting circuit 4.

[0030] When the image of a subject is sensed by the CCD 1, the videosignal representing the image of the subject is output from the CCD 1.The video signal output from the CCD 1 is subjected to CDS (correlateddouble sampling) processing in a CDS circuit 3, whence the resultantanalog video signal is applied to an analog/digital converting circuit4. The latter converts the analog video signal to digital image data.The image data resulting from the conversion is applied to the CPUs 5A,5B, 5C and 5D of the correction circuits 15A, 15B, 15C and 15D,respectively.

[0031] When image data based upon area A has been applied, the digitalstill camera is controlled by the CPU 5A so as to store this image datatemporarily in the SDRAM 7A of correction circuit 15A. Similarly,control is such that when image data based upon area B has been applied,this image data is stored temporarily in the SDRAM 7B of correctioncircuit 15B; when image data based upon area C has been applied, thisimage data is stored temporarily in the SDRAM 7C of correction circuit15C; and when image data based upon area D has been applied, this imagedata is stored temporarily in the SDRAM 7D of correction circuit 15D.

[0032] The image data that has been stored in the SDRAM 7A of firstcorrection circuit 15A is read out by the CPU 5A and is corrected usingthe correction value for area A stored in the correction-value memory6A. The corrected image is stored temporarily in the SDRAM 7A again.Similarly, image data that has been stored in the SDRAM 7B of the secondcorrection circuit 15B is corrected using the correction value for areaB and the corrected image data is stored in the SDRAM 7B; image datathat has been stored in the SDRAM 7C of the third correction circuit 15Cis corrected using the correction value for area C and the correctedimage data is stored in the SDRAM 7C; and image data that has beenstored in the SDRAM 7D of the fourth correction circuit 15D is correctedusing the correction value for area D and the corrected image data isstored in the SDRAM 7D. Accordingly, image data representing the imageobtained by correcting the image that was formed in area A is stored inSDRAM 7A of the first correction circuit 15A. Similarly, image datarepresenting the images obtained by correcting the images that wereformed in areas B, C and D is stored in SDRAM 7B of the secondcorrection circuit 15B, SDRAM 7C of the third correction circuit 15C andSDRAM 7D of the fourth correction circuit 15D, respectively.

[0033] The image data representing the image obtained by correcting theimage that was formed in area B, which image data has been stored inSDRAM 7B of the second correction circuit 15B, is read by the CPU 5B.The image data that has been read is stored in SDRAM 7A by the CPU 5A ofthe first correction circuit 15A. Similarly, image data representing theimage obtained by correcting the image that was formed in area C, whichimage data has been stored in the third correction circuit 15C, andimage data representing the image obtained by correcting the image thatwas formed in area D, which image data has been stored in the fourthcorrection circuit 15D, also is stored in SDRAM 7A of the firstcorrection circuit 15A. Thus, one frame's worth of corrected image datais stored in SDRAM 7A of the first correction circuit 15A.

[0034] The one frame of image data is read out of SDRAM 7A of the firstcorrection circuit 15A and is applied to an LCD (liquid crystal display)driver 8. An LCD 9 is driven by the LCD driver 8, whereby the image ofthe subject obtained by photography is displayed on the display screenof the LCD 9. Since a correction is applied in the manner describedabove, image disturbance at the area boundaries will not occur in theimage being displayed on the display screen of the LCD 9.

[0035] If a shutter-release button (not shown) is pressed, the correctedimage obtained as set forth above will be applied to and recorded on amemory card 11 via a card interface 10.

[0036]FIG. 4 is a flowchart illustrating correction processing.

[0037] If image data obtained from corresponding areas A through D isinput to CPUs 5A to 5D from the first to fourth correction circuits 15Ato 15D, respectively (“YES” at step 41), then the image data is storedin the SDRAMs 7A to 7D, respectively (step 42). The image data that hasbeen stored in respective ones of the SDRAMs 7A to 7D is corrected usingthe correction values corresponding to the areas A to D and stored inthe correction-value memories 6A to 6D (step 43). The corrected imagedata is stored in the SDRAMs 7A to 7D again (step 44).

[0038] This is followed by applying the image data, which has beenstored in the SDRAMs 7B to 7D, to the SDRAM 7A in the first correctioncircuit 15A, as described above, whereby image data representing oneframe of an image is generated. The corrected image is displayed on theLCD 9. Further, the corrected frame of image data is recorded on thememory card 11.

[0039]FIG. 5 is a block diagram illustrating the electrical structure ofa digital still camera according to another embodiment of the presentinvention. Components in FIG. 5 identical with those shown in FIG. 3 aredesignated by like reference characters and need not be described again.

[0040] The digital still camera shown in FIG. 5 is provided with firstto fourth CDS circuits 3A to 3D and first to fourth analog/digitalconverting circuits 4A to 4D corresponding to the first to fourthcorrection circuits 15A to 15D.

[0041] The video signal output from the CCD 1 is subjected to correlateddouble sampling processing in the first to fourth CDS circuits 3A to 3D,respectively. The video signal that has undergone correlated doublesampling is converted to digital image data in the first to fourthanalog/digital converting circuits 4A to 4D. The image data output fromthe first to fourth analog/digital converting circuits 4A to 4D is inputto the first to fourth correction circuits 15A to 15D, respectively,where the data is corrected.

[0042] The corrected image data corresponding to areas A to D is inputto a data processing circuit 51, where one frame of image data isgenerated. The image represented by the generated image data isdisplayed on the display screen of LCD 9 and the generated image data isrecorded on the memory card 11 as in the manner described above.

[0043] Since the above-described correction processing is carried outeven with a CCD 1 produced by performing exposure multiple times inareas A to D, image disturbance at the boundaries of the areas can beprevented.

[0044] As many apparently widely different embodiments of the presentinvention can be made without departing from the spirit and scopethereof, it is to be understood that the invention is not limited to thespecific embodiments thereof except as defined in the appended claims.

What is claimed is:
 1. An apparatus for correcting a solid-stateelectronic image sensing device, comprising: a solid-state electronicimage sensing device, which is created by dividing an image sensing areainto a plurality of areas, for outputting image data representing theimage of a subject by sensing the image of the subject; acorrection-value memory for storing correction values in associationwith respective ones of the plurality of areas of said solid-stateelectronic image sensing device; and an image-data correction unit forcorrecting image data, which is obtained based upon respective ones ofthe plurality of areas from among the image data that is output fromsaid solid-state electronic image sensing device, using correspondingcorrection values from among the correction values stored in saidcorrection-value memory.
 2. The apparatus according to claim 1, whereina plurality of said correction-value memories are provided inassociation with respective ones of the plurality of areas, and saidimage data correction unit includes: a plurality of correction circuitscorresponding to the plurality of said correction-value memories; and acontrol unit for applying image data obtained based upon respective onesof the plurality of areas from among the image data output from saidsolid-state electronic image sensing device to corresponding correctioncircuits from among the plurality of correction circuits, andcontrolling said correction circuits so as to correct the image datausing corresponding correction values from among the correction valuesthat have been stored in said plurality of correction-value memories. 3.The apparatus according to claim 2, wherein said solid-state electronicimage sensing device includes: a solid-state electronic image-sensingelement, which is created by dividing an image sensing area into aplurality of areas, for outputting a video signal representing the imageof a subject by sensing the image of the subject; and a plurality ofanalog/digital converting circuits provided in association with theplurality of areas for converting, to respective ones of items of imagedata, video signals obtained based upon respective ones of the pluralityof areas from the video signal output from said solid-state electronicimage sensing element.